Pen



FIG. 1 is a front elevation view of a pen in accordance with my design;

FIG. 2 is left side view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a top view thereof; and,

FIG. 5 is a bottom view thereof.

The rear elevation view is a mirror image of the front elevation view. 

The ornamental design for a pen, as shown and described. 